This invention relates to polyurethane flexible block foams which are flame-laminable and have high peel strength, a process for their production and the use thereof for textile lamination.
Webs of foam produced from polyurethane foam blocks by cutting processes are often used for lamination with many different kinds of textiles for various applications. This is carried out by a bonding or surface melting process, such as flame lamination. Due to their particular suitability, polyester-polyurethane foams are typically used for conventional flame lamination. The ester groups in the polyol component result in a good hot-melting behavior with optimal setting behavior; and the foams exhibit an exceptionally strong bonding to textiles. Such polyester-polyurethane foam/textile laminates have peel strengths of 18 to 22 N, in accordance with DIN 53 357. Moreover, they exhibit elongations at break of about 300% and tensile strengths of about 200 kPa, and accordingly, permit high laminating speeds. Furthermore, at certain bulk densities such polyester foams are self-extinguishing in accordance with FMVSS 302 (SE). Therefore, polyester foams are mainly used as foamed-plastic film for the lamination process. However, their fogging behavior in accordance with DIN 75 201 is unfavorable. This is due to the method of production of the polyester polyols which results in the presence of fogging-active low-molecular components in the polyester polyols. They also have a high proportion of closed cellular structures.
An alternative is the use of polyether foams. These, however, do not have a satisfactory laminability. Various methods of increasing the laminability of polyether foams have been proposed.
Thus, in EP-A 25 549, the addition of neopentyl glycol hydroxypivalate ester during the production of the foam is proposed. This results in good laminability and a good high-frequency weldability, but high values for the compression set are obtained even at bulk densities which are relatively high for ether foams.
EP-A 35 687 discloses the use of solutions of reaction products of diisocyanates with diprimary diols in high-molecular polyethers having mainly secondary hydroxyl groups for the production of flame-laminable foams. However, the foams thus obtained are not resistant to aging. Thus, for example, a poorer recovery after continuous stress is found. These disadvantages are even more marked at lower bulk densities and when flameproofing agents are added in order to achieve self-extinguishing properties.
U.S. Pat. Nos. 5,891,928 and 5,900,087 describe the addition of aliphatic diols or polymeric diols to polyether foam formulations in order to improve the flame laminability. However, the resulting peel strengths of the laminated parts, at 8 to 14 N, are significantly less than those of the laminated polyester foams, which attain values of 18 to 22 N. Experience shows that a peel strength of approximately 16 N is required for a good adhesion.
It has now been found that, the addition of aromatically modified glycols or aromatically modified ether glycols, it is possible to produce flame-laminable ether foams whose peel strength, tensile strength and elongation at break are comparable with those of polyester foams, and which moreover exhibit the favorable aging and fogging behavior of polyether foams. This is true even in the case of foams which have been made self-extinguishing in compliance with FMVSS 302.
The invention provides flame-laminable polyether-polyurethane foams, which comprise the reaction product of:
A) at least one polyisocyanate or polyisocyanate prepolymer; with
B) at least one polyether polyol having a functionality of 2 to 6 and a number average molecular weight of 1,000 to 10,000 g/mole;
C) optionally, one or more aliphatic chain extenders having a molecular weight of 62 to 800;
D) at least one aromatic polyol component that is at least bifunctional;
E) a blowing agent comprising water, and optionally, CO2, which is preferably present in liquid form, and/or other organic blowing agents;
F) optionally, one or more stabilizers;
G) optionally, one or more activators; and
H) optionally, one or more flameproofing agents and other additives.
The aromatic polyol components that are at least bifunctional, i.e. component D) above, result in flame-laminable polyether polyurethane foams.
The present invention also relates to a process for the production of a flame-laminable polyether-polyurethane foam. This process comprises reacting:
A) at least one polyisocyanate or polyisocyanate prepolymer; with
B) at least one polyether polyol having a functionality of 2 to 6 and a number average molecular weight of 1,000 to 10,000 g/mole;
C) optionally, one or more aliphatic chain extenders having a molecular weight of 62 to 800;
D) at least one aromatic polyol component that is at least bifunctional;
E) a blowing agent comprising water, and optionally, CO2, which is preferably present in liquid form, and/or other organic blowing agents;
F) optionally, one or more stabilizers;
G) optionally, one or more activators; and
H) optionally, one or more flameproofing agents and other additives.
The present invention also relates to a process for the production of a composite material comprising laminating a layer of polyether-polyurethane foam with a textile layer.
In the process according to the present invention, organic di- or polyisocyanates or polyisocyanate prepolymers are suitable for component A). Suitable di- or polyisocyanates include, for example, aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates, such as are described in Justus Liebigs Annalen der Chemie, 562 (1949) 75, for example, those corresponding to the formula:
Q(NCO)n 
wherein:
n represents an integer from 2 to 4, preferably 2, and
Q represents an aliphatic hydrocarbon group having 2 to 18 carbon atoms, preferably 6 to 10 carbon atoms, a cycloaliphatic hydrocarbon group having 4 to 15 carbon atoms, preferably 5 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 15 carbon atoms, preferably 6 to 13 carbon atoms, or an araliphatic hydrocarbon group having 8 to 15 carbon atoms, preferably 8 to 13 C atoms.
Polyisocyanates of the type described in U.S. Pat. No. 4,263,408, the disclosure of which is herein incorporated by reference, are preferred. As a rule, the technically readily accessible polyisocyanates are particularly preferred such as, for example, 2,4-and 2,6-tolylene diisocyanate as well any mixtures of these isomers (xe2x80x9cTDIxe2x80x9d), polyphenyl polymethylene polyisocyanates, as produced by aniline-formaldehyde condensation and subsequent phosgenation (xe2x80x9ccrude MDIxe2x80x9d), and polyisocyanates containing carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups (xe2x80x9cmodified polyisocyanatesxe2x80x9d), in particular those modified polyisocyanates which are derived from 2,4- and/or 2,6-tolylene diisocyanate or from 4,4xe2x80x2- and/or 2,4xe2x80x2-diphenylmethane diisocyanate. Prepolymers of the above-mentioned isocyanates and organic compounds having at least one hydroxyl group may also be used. Examples of compounds having at least one hydroxyl groups which may be given are polyols or polyesters having one to four hydroxyl groups and (number average) molecular weights of 60 to 1,400. Most preferably used are the technically obtainable polyisocyanates by the name of xe2x80x9cpolymeric diphenylmethane diisocyanatexe2x80x9d, having a functionality of higher than 2.0, as well as prepolymers produced from them.
In accordance with the present invention, polyol component B) comprises at least one polyether polyol (i.e. a poly(oxyalkylene) polyol) having a functionality of from about 2 to about 6 and a number average molecular weight of from about 1,000 to about 10,000 g/mole. Mixtures of such polyols may also be used as component B).
The poly(oxyalkylene) polyols sutiable for the present invention include those which can be prepared by, for example, the polyaddition of one or more alkylene oxides to one or more polyfunctional starter compounds in the presence of one or more basic catalysts. Preferred starter compounds include those molecules having from about two to about six hydroxyl groups per molecule such as, for example, water, triethanolamine, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol, mannitol or sorbitol.
Other possible starter compounds for the component B) of the present invention include, for example, ammonia or compounds which have at least one primary or secondary amino group such as, for example, aliphatic amines including, for example, 1,2-diaminoethane, oligomers of 1,2-diaminoethane (for example, diethylenetriamine, triethylenetetramine or pentaethylenehexamine), ethanolamine or diethanolamine, 1,3-diaminopropane, 1,3-diaminobutane, 1,4-diaminobutane, 1,2-diaminohexane, 1,3-diaminohexane, 1,4-diaminohexane, 1,5-diaminohexane, 1,6-diaminohexane, aromatic amines such as 1,2-diaminobenzene, 1,3-diaminobenzene, 1,4-diaminobenzene, 2,3-diaminotoluene, 2,4-diaminotoluene, 3,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, 2,2xe2x80x2-diaminodiphenylmethane, 2,4xe2x80x2-diaminodiphenylmethane, 4,4xe2x80x2-diaminodiphenylmethane or aromatic amines which are obtained by acid-catalyzed condensation of aniline with formaldehyde. These starter compounds may be used alone or as a mixture.
Alkylene oxides preferably used for the preparation of the poly(oxyalkylene)polyols in accordance with the invention include oxirane, methyloxirane and ethyloxirane. These alkylene oxides may be used alone or as a mixture. When used as a mixture, the alkylene oxides can be reacted statistically or blockwise or both in succession. Further details may be found in xe2x80x9cUllmanns Encyclopxc3xa4die der industriellen Chemiexe2x80x9d, Volume A21, 1992, p. 670 ff.
Other suitable poly(oxyalkylene) polyols to be used as component B) of the present invention include, for example, dispersions of a grafted polymerization product in a poly(oxyalkylene) polyol according to the invention. This polymerization product can be prepared, for example, by free-radical in-situ polymerization of, for example, acrylonitrile and/or styrene in a poly(oxyalkylene) polyol in accordance with the method described in, for example, U.S. Pat. No. 3,523,093, the disclosure of which is herein incorporated by reference. Other suitable polymerization products include, for example, polyurethanes containing tertiary amino-groups, polyurea compounds or polyhydrazides. Suitable methods for preparing dispersions of these polymerization products are described in, for example, U.S. Pat. No. 4,304,708 and U.S. Pat. No. 4,374,209, the disclosures of which are herein incorporated by reference, and DE-OS 32 31 497. The proportion of the polymeriszation products in the dispersion is preferably 1 to 50 wt. %.
Further examples of suitable polyols which can be contained in the polyol component B) include polyfunctional alcohols, amines, amino alcohols, or mixtures of these, as well as their oxypropylated and/or oxyethylated derivative products.
Suitable compounds to be used as component C) the chain extender, include, for example, those aliphatic organic compounds having a molecular weight (Mn) of 62 to 800 g/mole such as, for example, glycerol, glycols, sorbitol and alkanolamines.
In accordance with the present invention, low molecular weight aromatic polyols which are at least bifunctional are used as flame lamination additives, i.e. component D). Suitable aromatic compounds for component D) include both aromatic polyester polyols and aromatic polyether polyols. These aromatic polyols, besides containing a relatively short-chain aliphatic ether portion, preferably also have aromatically bonded ester or ether groupings. If aromatic polyether polyols are used, these preferably have a number average molecular weight of from about 150 to about 999 g/mole, and more preferably from about 150 to about 700 g/mole. Suitable polyester polyols preferably have number average molecular weights of from about 150 to about 1,200 g/mole, and more preferably from about 150 to about 1,000 g/mole.
Some examples of suitable aromatic polyester polyols include those compounds composed of at least bifunctional aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid or even higher functional carboxylic acids such as trimellitic acid, trimesic acid, the carboxyl groups of which are esterified with glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, triethylene glycol, higher homologues of these glycols, butylene glycol, or higher functional alcohols such as, for example, glycerol or trimethylolpropane. Aromatic polyester polyols having at least two OH groups and an ester group and an extended phenolic OH group can also be used. Examples of such compounds include 4-(2-hydroxyethoxy)benzoic acid, 2-hydroxyethyl ester or 4-(2-hydroxyethoxy)benzoic acid, 2-hydroxyethoxyethyl ester.
Suitable aromatic polyether polyols include those compounds which are prepared by, for example, the alkoxylation of at least bifunctional aromatic phenol derivatives such as, for example, 2,2-bis(4-hydroxy-phenyl)propane, hydroquinone, dihydroxynaphthalene, catecol, resorcinol, dihydroxybiphenyl, bis(hydroxyphenyl)methane, dihydroxydiphenyl ether, hydroxymethylbenzyl alcohol, by means of alkylene oxides such as, for example, ethylene oxide, propylene oxide or butylene oxide, by the method known in principle to the person skilled in the art.
These flame lamination additives, i.e. component D), are preferably used in quantities of from about 1 to about 20% by wt., based on the combined weight of the components B) and C).
In accordance with the present invention, component E) the blowing agent(s) comprises water. Preferably, water is used as a chemical blowing agent which, by reaction with isocyanate groups, delivers carbon dioxide as fuel gas. Water is preferably present in a quantity of from about 1.0 to about 6.0% by wt., preferably from about 1.5 to about 5.5% by wt., based on the combined weight of components B), C) and D). In addition to water, component E) may also comprise one or more non-combustible physical blowing agents such as, for example, carbon dioxide, particularly in liquid form. In principle, blowing agents from the class of the hydrocarbons may also be used. Examples of such hydrocarbons include compounds such as, for example, the C3-C6-alkanes such as, for example, butanes, n-pentane, isopentane, cyclopentane, hexanes and the like. Also suitable are the halogenated hydrocarbons such as, for example, dichloromethane, dichloromono-fluoromethane, chlorodifluoroethane, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-dichloro-2-fluoroethane, and more preferably are the chlorine-free fluorocarbons such as, for example, difluoromethane, trifluoromethane, difluoroethane, 1,1,1,2-tetrafluoroethane, tetrafluoroethane (R 134 or R 134a), 1,1,1,3,3-pentafluoropropane (R 245fa), 1,1,1,3,3,3-hexafluoropropane (R 356), 1,1,1,3,3-penta-fluorobutane (R 365mfc), heptafluoro-propane or even sulfur hexafluoride. Mixtures of these blowing agents may also be used. Other suitable blowing agents include carboxylic acids such as, for example, formic acid, acetic acid, oxalic acid, and chemical blowing agents which release gases in the course of the foaming process, such as, for example, azo compounds. These blowing agents are preferably used in combination with water.
Polyethersiloxanes, preferably water-soluble polyethersiloxanes, are primarily suitable compounds to be used as stabilizers, component F), in accordance with the present invention. These compounds are generally synthesized in such a way that one long-chain copolymer of ethylene oxide and propylene oxide is bonded to a polydimethylsiloxane group. Other suitable foam stabilizers are described in, for example, U.S. Pat. Nos. 2,834,748, 3,629,308 and 2,917,480, the disclosures of which are herein incorporated by reference.
Examples of suitable compounds to be used as activators, i.e. component G), in accordance with the present invention include tertiary amines, such as triethylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethyl-ethylenediamine, pentamethyldiethyltriamine and higher homologues (as described in, for example, U.S. Pat. No. 4,143,003, the disclosure of which is herein incorporated by reference, and DE-A 26 24 528), 1,4-diazabicyclo-[2.2.2]octane, N-methyl-Nxe2x80x2-dimethylaminoethylpiperazine, bis(dimethylaminoalkyl)piperazine, N,N-dimethyl-benzylamine, N,N-dimethylcyclohexylamine, N,N-diethylbenzylamine, bis(N,N-diethylaminoethyl) adipate, N,N,Nxe2x80x2,Nxe2x80x2-tetramethyl-1,3-butanediamine, N,N-di-methyl-xcex2-phenylethylamine, 1,2-dimethylimidazole, 2-methylimidazole, monocyclic and bicyclic amidines and bis(dialkylaminoalkyl) ethers such as, for example, 2,2-bis(dimethylaminoethyl) ether.
Organometallic compounds, in particular organotin compounds, are also suitable to be used as activators, component G) of the present invention. Besides sulfur-containing compounds such as di-n-octyltin mercaptide, preferred organotin compounds include, for example, tin(II) salts of carboxylic acids, such as, for example, tin(II) acetate, tin(II) octoate, tin(II) ethylhexoate and tin(II) laurate, and the tin (IV) compounds such as, for example, dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate or dioctyltin diacetate.
Compounds suitable for use as a flameproofing agents, i.e. component H) of the present invention include, for example, tricresyl phosphate, tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, tetrakis(2-chloroethyl)ethylene diphosphate, dimethyl methanephosphonate, diethyl diethanolamino-methylphosphonate, tris(dipropylene glycol) phosphite, tris-(dipropylene glycol) phosphate, bis(2-hydroxyethyl)ethylene glycol diphosphate bis(2-chloroethyl) ester and halogen-containing, flameproofing polyols. Additional examples of optionally concomitantly used components fpr H) include foam stabilizers and cell regulators, reaction inhibitors, stabilizers, plasticizers, dyes and fillers as well as fungistatic and bacteriostatic substances. These are in most cases added to the polyol component in quantities of 0 to 10 parts by weight, preferably 2 to 6 parts by weight.
Details concerning the method of use and mechanism of action of these additives are given in G. Oertel (Ed.) xe2x80x9cKunststoff-Handbuchxe2x80x9d, Volume VII, Carl Hanser Verlag, Third edition, Munich 1993, pp. 110-115.
The foams according to the invention are generally produced by intensively mixing together the di- or polyisocyanate A) as one component, and a mixture of the remaining constituents as the other component by means of a suitable, usually mechanical, device. The foams can be produced either continuously, for instance, on a conveyor belt, or in batches. The production of flexible foams is known in principle to the person skilled in the art and is described in, for example, in G. Oertel (Ed.) xe2x80x9cKunststoff-Handbuchxe2x80x9d, Volume VII, Carl Hanser Verlag, Third edition, Munich 1993, pp. 193-220.
The production of foams is preferably carried out in such a way that the NCO/OH index, that is, the stoichiometric ratio of reactive isocyanate groups to hydroxyl groups, is between 0.80 and 1.20. The NCO/OH index is more preferably between 0.90 and 1.15. The bulk density of the resulting moldings is preferably 15 kg/mxe2x88x923 to 55 kg/mxe2x88x923, and more preferably 20 kg/mxe2x88x923 to 50 kg/mxe2x88x923.
The present invention also relates to textile/foam composite materials (i.e. laminates) produced using the foams according to the invention. In conventional processing, these composite materials are produced by joining together the melted layer of foam and the textile top layer. To this end, the polyether-polyurethane foams according to the invention, after a short-time flame treatment, are bonded to a textile covering made of a textile comprising, for example, polyamide, polyester, cotton or leather, to yield composites with permanent high peel strength. It is usual to apply a charmeuse protective fabric to the foam. Another method of producing the laminates of the present invention comprises bonding the foams according to the invention to the textile top layer using hot-melt adhesives by the known per se hot-melting technique, or by means of dispersion adhesives.
The following examples further illustrate details for the process of this invention. The invention, which is set forth in the foregoing disclosure, is not to be limited either in spirit or scope by these examples. Those skilled in the art will readily understand that known variations of the conditions of the following procedures can be used. Unless otherwise noted, all temperatures are degrees Celsius and all percentages are percentages by weight.